It's become popular in some modern circles to claim that a large percentage of the New Testament was attributed to the wrong author. It's common for scholars to argue that something like fifteen, eighteen, or more of the books of the New Testament are wrongly attributed. Some skeptics, though a small minority and usually of the more ignorant variety, even go as far as to claim that every New Testament book has been attributed to the wrong author. (Hebrews would be an exception if considered anonymous in its attribution, but not if considered a work attributed to somebody like Paul or Barnabas.) I've discussed some of the problems with such conclusions in many past articles, such as here and here.
Often, critics are inconsistent in their skepticism. The same critic who claims that the textual evidence for the New Testament documents is insufficient, or rejects an authorship attribution as reasonable as Mark's authorship of the second gospel, for example, will accept the text and authorship attributions of many extra-Biblical documents that have comparable or worse evidence, like the Annals of Tacitus. Many critical arguments against Christianity, such as the use of Josephus and Tacitus to argue against the census account of Luke 2, depend on an acceptance of extra-Biblical sources that's far less critical of those sources than the Biblical sources. I've written about such double standards elsewhere, such as here and here. Craig Keener, commenting on attempts to deny that the same author wrote the gospel of John and the epistles of John, writes:
"No other author of antiquity could survive the nit-picking distinctions on which NT [New Testament] scholars, poring over a smaller corpus, often thrive. As a translator of Euripides for the Loeb series notes, Euripides’ 'plays, produced at times widely apart, and not in the order of the story, sometimes present situations (as in Hecuba, Daughters of Troy, and Helen) mutually exclusive, the poet not having followed the same legend throughout the series.' He would not fare well in the hands of our discipline." (The Gospel Of John: A Commentary, Vol. 1 [Peabody, Massachusetts: Hendrickson Publishers, 2003], p. 125)
Last night, in the process of looking for some material to post in another thread, I came across something I wrote about ten years ago. I noticed that there were a lot of differences between how I wrote then and how I write now (vocabulary, argumentation, documentation, etc.). Glenn Miller, in his piece on pseudonymity, notes some variation in his own writing style. He compares the writing in articles he wrote several years earlier to the writing in his latest articles. You can notice some differences. That's one of the reasons why external evidence is so significant. It's more conclusive than internal evidence.
Many people, including scholars, are overly cynical, and often their cynicism is selective. I recently listened to John Piper's biographical sketch of George Whitefield. In it, he comments on a Whitefield biography written by a historian:
"Harry Stout, professor of history at Yale, is not as sure about the purity of Whitefield’s motives as Sarah Edwards was. His biography, The Divine Dramatist: George Whitfield and the Rise of Modern Evangelicalism, is the most sustained piece of historical cynicism I have ever read. In the first 100 pages of this book, I wrote the word cynical in the margin 70 times."
Many people approach the Bible in a manner similar to or worse than how Stout approached Whitefield. But being critical of Christianity, the New Testament, religion, or some other such subject isn't enough. Being wrong is a bad thing, regardless of whether the error occurs in a religious or a non-religious direction. Non-religious gullibility isn't a sufficient substitute for religious gullibility. There's a danger in believing that Mark wrote the second gospel if he didn't actually write it, but there's also a danger in believing that Mark didn't write the second gospel if he actually did write it.
Kent Clarke is an example of a New Testament scholar who believes that some New Testament documents are falsely attributed, but thinks that some of his colleagues have gone too far in their conclusions on the issue. Traditional conservative Christians aren't alone in making such observations.
Clarke writes of one scholar, "by rejecting the authenticity of most New Testament works, Rist has also dismissed much sound historical scholarship." (in Lee McDonald and James Sanders, edd., The Canon Debate [Peabody, Massachusetts: Hendrickson Publishers, 2002], p. 446) He refers to "modern scholarship's proclivity for applying a wide range of interpolative and composite theories to most ancient literature" (n. 36 on p. 447). Concerning F.C. Baur, Clarke comments:
"In time, however, Baur would come to regard all but the first four Pauline letters as pseudonymous, along with the seven General Epistles. Baur's defense of pseudonymity was just as novel as the extent of his pseudonymous declarations, for he was first to assert that antiquity regarded pseudonymity as an acceptable literary convention not undertaken with the intent to deceive. 'With few exceptions,' notes Ellis, speaking of Baur and the Tubingen school, 'they are the root of all subsequent scholarship that assigned pseudepigraphal authorship to New Testament documents....[T]he Baur hypothesis became the Baur tradition.'...Guthrie ('Idea of Canonical Pseudepigrapha,' 21) remarks, 'The fact is that Baur's literary criticism was dominated by his dogmatic presuppositions and since these had to be maintained at all costs, it was no embarrassment that pseudepigraphic writings became more normal in the extant Pauline canon than genuine works.'...A. Julicher, like Baur, was able to minimize the notion of deceit inherent to pseudonymity by arguing that the idea of 'intellectual property' was a modern construct all but absent from antiquity, and that Christian writers could, with the best intentions, place into the mouths of the apostles a contemporising message....Arguments against the concept of intellectual property in antiquity have become common fair in discussions of pseudonymity, and can be found in more recent examples like A.T. Lincoln...This theory has, however, been debunked by Speyer (Die literarische Falschung, 175-76), who has clearly shown the presence of such a concept in antiquity." (pp. 458-459, n. 86 on p. 458, 459, n. 90 on p. 459)
See also here.